This invention relates to a containment for a continuous flow machine. The invention further relates to a continuous flow machine, an aircraft engine and a calculation method for the design of a containment.
In continuous flow machines, in particular in gas turbines, a structural failure of a component can lead to a penetration of the housing and thus the ejection of a part of this component out of the continuous flow machine by centrifugal force. In particular, in the event of the breakage of a blade of a continuous flow machine, the blades can be ejected at high speed from the housing of the continuous flow machine and then damage machinery and/or injure persons in the vicinity. For this reason, the housing of a continuous flow machine is designed so that it has a wall thickness and therefore a resistance to penetration that can at least largely prevent a penetration of the housing by a part in the event of a structural failure of a component. For this purpose, for example, the housing can be provided with additional parts of a containment and/or can itself be designed as the protective device. A protective device of this type is also called a containment or an engine containment.
EP 2 551 467 A1, for example, describes a housing of a continuous flow machine which is designed so that it has sections of lower radial wall thickness and sections of greater radial wall thickness. The areas of greater radial wall thickness are thereby located in an axial area of the continuous flow machine in which respective blade rows are located. Blade rows of this type are particularly subject to structural failure because they generally rotate at a high rate of speed around an axial longitudinal axis of the flow machine and particularly strong centrifugal forces are exerted on the individual blades.
One disadvantage of a containment of this type is that the sections of greater wall thickness result in corresponding additional weight. However, light weight is important especially when the continuous flow machine is used as an engine. In particular when the continuous flow machine is used as an aircraft engine, the fuel consumption of the corresponding aircraft can be particularly high as a result of a particularly heavy housing or a particularly heavy containment. In the event of an unfavorable axial position of the areas of greater and lesser wall thicknesses, the housing can still be penetrated if, in the event of a structural failure, part of a component impacts an area of lesser wall thickness.
The object of the present invention is therefore to create a containment for a continuous flow machine with which the continuous flow machine is particularly lightweight and safe. An additional object of the present invention is to create a continuous flow machine and an aircraft engine that are each particularly lightweight and safe.
Advantageous configurations with appropriate developments of the invention are disclosed in the individual subclaims, wherein advantageous configurations of the individual devices and of the calculation process are to be considered advantageous configurations of the respective other devices and of the calculation method and vice-versa.
A first aspect of the invention relates to a containment for a continuous flow machine, in particular a gas turbine, with at least one annular housing by means of which a flow chamber of the continuous flow machine can be at least partly bounded radially outwardly and that has at least one axial section with a lesser radial wall thickness and at least one axial section adjacent to it with a greater radial wall thickness. The axial direction is thereby defined by an axial longitudinal axis of the continuous flow machine, in particular by a shaft of the continuous flow machine. The radial direction is accordingly orthogonal to this longitudinal axis. An axial and a radial direction of the protection apparatus are thereby defined by the installation orientation of the containment on the continuous flow machine and thereby correspond to the axial and radial direction of the continuous flow machine.
The containment according to the invention is characterized in that the housing is configured so that the section with a greater wall thickness is at a distance in the axial direction of the continuous flow machine from a trailing edge of a guide vane that lies downstream in the direction of flow of the continuous flow machine and extends downstream in the direction of flow of the continuous flow machine over a leading edge of the next downstream guide vane. In particular, the section of greater wall thickness is at some distance downstream in the axial direction from the trailing edge of the guide vane. The direction of flow is thereby defined by a gas flow through individual stages of the continuous flow machine, in particular by a gas flow through the flow chamber. The direction of flow is conventionally parallel to the longitudinal axis of the continuous flow machine. The guide vanes are each stationary vanes, while the respective rotor blades are rotating blades of the continuous flow machine. The guide vane can also be part of a guide vane ring and correspond to the trailing edge and the leading edge of one edge of the guide vane ring. The flow chamber is a section of the gas turbine through which gas flows, e.g. a compressor, a combustion chamber and/or a turbine.
On known containments for continuous flow machines, it was assumed that individual rotor blades strike the housing in an axial section in which they are located. At the same time, it was assumed that individual guide vanes block a trajectory in the axial direction of a part in the event of a structural failure of a component of the continuous flow machine. Correspondingly, there was no expectation of an impact in the axial sections corresponding to the guide vanes by a part in the event of a structural failure. Therefore no sections of greater wall thickness were provided at that point in the housing. However, it has surprisingly been shown that there can also be an impact of a part with the housing at least in a section of the axial dimension of the guide vanes.
Therefore it is necessary on one hand to extend the section with a greater wall thickness over an axial longitudinal area that is long enough so that it extends to the next guide vane downstream, with an at least partial radial overlap with a rotor blade corresponding to the section of greater wall thickness. It has simultaneously been found that it is not necessary to extend the axial section of greater wall thickness upstream so far that, viewed from the rotor blade corresponding to the section of greater wall thickness, it extends to the next upstream guide vane. Overall, therefore, the axial section with a greater wall thickness is shifted axially downstream compared to known containments. Consequently the containment is particularly safe. Because the possible trajectory of the part in the event of a structural failure is taken into consideration and simulated during the design of the containment, the axial section of greater wall thickness can be adapted particularly effectively to the actual requirements. Thus the axial section of greater wall thickness can extend over a particularly small axial section and consequently the containment can be particularly lightweight.
In individual sections of greater wall thickness at the beginning or end of the continuous flow machine or of an individual section at the beginning or end of a compressor, combustion chamber or turbine, for example, the housing is on the other hand frequently supported and/or protected by surrounding structural components of the continuous flow machine, at least in the terminal area. The continuous flow machine is at that section provided with particular protection against an ejection of parts. Therefore it is precisely in a middle section that the above-mentioned advantageous positioning and/or extension of the axial section of greater wall thickness is particularly important and results in a particularly large savings of weight and/or particularly effective protection.
The section of lesser wall thickness can be also only indirectly adjacent to the section of greater wall thickness. An intermediate area or transitional area can thereby be provided between the sections of lesser wall thickness and greater wall thickness. This intermediate area or transitional area is preferably no longer in the axial direction than 300%, in particular 100%, of the difference in the wall thickness of the section of greater wall thickness and the indirectly adjacent area of lesser wall thickness.
In an additional advantageous configuration of the containment according to the invention, the section of greater wall thickness begins at some distance downstream in the axial direction from the trailing edge of the guide vane and begins at a distance of from 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or 55% to 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%, preferably 20% to 30%, of a cord length of this guide vane. In this manner a particularly safe containment can be created, which is particularly lightweight on account of a particularly late beginning of the axial section of greater wall thickness downstream in the direction of flow.
In an additional advantageous configuration of the containment according to the invention, the section of greater wall thickness, in the axial direction downstream behind the leading edge of the next downstream guide vane, ends with a radial overlap of from 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or 55% to 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%, preferably 20% to 30%, of the cord length of this next guide vane downstream. As a result of this particularly appropriate dimension of the axial section of greater wall thickness in the downstream direction, a penetration of the housing by a part of the component of the continuous flow machine, in the event of a structural failure of the component, can be prevented at least to a large extent in an axial section in which previously there was no protection. It has thereby been demonstrated that in the event of a structural failure, parts can penetrate up to this depth in the axial direction into the axial section of a guide vane ring where they can potentially penetrate the housing. A correspondingly designed containment therefore makes it possible to create a particularly safe continuous flow machine.
In an additional advantageous configuration of the containment according to the invention, the containment has a plurality of sections of greater wall thickness and sections of lesser wall thickness alternating in the axial direction, where the number of sections of greater wall thickness corresponds to a number of rotor blade rings. The rotor blade stages are components that are particularly threatened by structural failure, which can also impact the containment housing with a particularly high level of kinetic energy. A corresponding number of axial sections of greater wall thickness makes possible a particularly appropriate configuration of the housing. In particular, the containment can thus be lightweight and guarantee safe operation of the continuous flow machine.
In an additional advantageous configuration of the containment, there are sections with a lesser wall thickness adjacent to the at least one section of greater wall thickness both upstream and downstream. Sections of lesser wall thickness—given the use of identical materials—are generally lighter in weight than sections of greater wall thickness having the same axial dimension. Accordingly, it is particularly appropriate to limit the section of greater wall thickness to a specific axial section, and then to provide axial sections of lesser wall thickness to reduce weight.
In a further advantageous configuration of the containment according to the invention, the containment has a number of sections of greater wall thickness and sections of lesser wall thickness alternating with each other in the axial direction, where the housing, in an area that at partly forms the radially outer boundary of a turbine section of the continuous flow machine, has a section of greater wall thickness located downstream in the axial direction, the wall thickness of which is greater than in a respective preceding section of greater wall thickness. In other words, the individual wall thickness of the sections of greater wall thickness increases with the direction of flow. As a result, the containment can be particularly lightweight and safe.
In particular on a turbine of the continuous flow machine, the diameter of the individual rotor blade rings increases in the downstream direction. Accordingly, the configuration of the containment described above is particularly effective here. This effect can be reversed on a compressor of the continuous flow machine. In this case the rotor blades lying upstream are subjected to the highest forces and/or loads. Accordingly, it can be appropriate here for the housing, in a section of greater wall thickness lying downstream in the axial direction, to have a lesser wall thickness than in a respective preceding section of greater wall thickness. Therefore, even in a compressor, the configuration of the containment can be optimally adapted to the load. This system thereby applies only for those sections of greater wall thickness that are associated with respective rotor blades fastened to a common shaft. If the continuous flow machine is a multiple-shaft aviation engine, for example, individual sequential rotor blade rings can be located on different shafts and can therefore operate at different speeds of rotation. Therefore the loads and/or forces exerted on these rotor blade rings are no longer proportional to their axial position in the continuous flow machine. Accordingly, at a transition in the axial direction from a rotor blade ring on a first shaft to a rotor blade ring on a second shaft, there can also be a difference in wall thickness between different successive sections of greater wall thickness which does not correspond to their sequence or axial position.
In a further advantageous configuration of the containment according to the invention, the section of lesser wall thickness with the highest wall thickness has a lower wall thickness than the section of greater wall thickness with the lowest wall thickness. The section of greater wall thickness is therefore particularly resistant to penetration, while the section of lower wall thickness can be particularly lightweight.
In a further advantageous configuration of the containment according to the invention, at least one transitional area between the sections of greater wall thickness and the adjacent sections of lesser wall thickness has a surface curvature in a meridian section of the continuous flow machine, wherein the transitional area extends over an axial length of at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 215%, 220%, 225%, 230%, 235%, 240%, 245%, 250%, 255%, 260%, 265%, 270%, 275%, 280%, 285%, 290%, 295%, or 300%, preferably 100%, of a difference between the wall thickness of the section of greater wall thickness and the adjacent section of lesser wall thickness. As a result of a curved transition area of this type, the housing is particularly robust. Otherwise, in the event of abrupt changes in the wall thickness along the radial direction, this could represent a type of weak point in a housing that reduces the containment effect. The section of lesser wall thickness is then only indirectly adjacent to the section of greater wall thickness, because the two sections are separated from one another by the transitional area.
A curved transitional area of this type can also make it possible to create a particularly lightweight and particularly safe containment. In the event of a structural failure, it is also possible that a part will impact the transitional area. In the event of a structural failure, however, this part can have a lower kinetic energy than parts that impact in the axial section of greater wall thickness. Accordingly, the wall thickness in the transitional area can be greater than in the section of lesser wall thickness, although a lesser wall thickness is necessary than in the section of greater wall thickness. As a result of the presence of a transitional area with the surface curvature in a meridian section of the flow machine, the wall thickness of the housing can be designed in a manner particularly appropriate to the needs of the specific situation.
In an additional advantageous configuration of the containment according to the invention, the housing, in the section of lesser wall thickness and/or the section of greater wall thickness, can have a constant wall thickness over its axial dimension. Sections of the housing with a constant wall thickness are particularly simple and economical to fabricate.
In an additional advantageous configuration of the containment of the invention, the section of greater wall thickness and the section of lesser wall thickness can be formed jointly by one housing element of the housing. The different sections of lesser wall thickness and greater wall thickness can therefore be integrated into a single component. The fabrication of a housing of this type can be particularly economical and a housing of this type is particularly simple to assemble and install.
In an additional advantageous configuration of the containment according to the invention, the section of lesser wall thickness is formed by a housing element, and the section of greater wall thickness is formed by the housing element and at least one additional element located on it. The additional element can be in the form of a retaining ring, for example. The housing element can therefore be particularly easy to design, in particular with a continuous and essentially constant wall thickness. For example, additional elements can be replaced if they become damaged. The containment designed in this matter is therefore particularly easy to service and repair.
In an additional advantageous configuration of the containment according to the invention, the at least one additional element is made of a material that is different from that of the housing element. In the axial section of greater wall thickness, individual material characteristics can thereby be particularly well adapted to the specific requirements in the event of a structural failure. In particular, a material can be used that has a particularly high resistance to impacts by a part in the event of a structural failure. The containment can thus be particularly lightweight and/or particularly safe. For example, the additional element can be made of a ceramic material. In particular, the additional element can be in the form of a ceramic retaining ring. Alternatively or in addition, the additional element can also comprise a composite fiber material, for example. On the other hand, the housing element can be made of a metal alloy.
A second aspect of the invention relates to a continuous flow machine with at least one guide vane ring, at least one rotor blade stage and with at least one containment. The containment according to the invention is a containment according to the first aspect of the invention. The features and advantages that result from the use of the containment according to the first aspect of the invention are presented in the descriptions of the first aspect of the invention, where advantageous configurations of the first aspect of the invention are to be considered advantageous configurations of the second aspect of the invention and vice versa.
A third aspect of the invention relates to an aviation engine with a continuous flow machine according to the second aspect of the invention or with a containment according to the first aspect of the invention. The resulting particularly low weight is advantageous especially on an aviation engine because the fuel consumption of an aircraft can be kept particularly low. Moreover, the containment of an aviation engine must be particularly safe, because a penetration of the housing can have particularly serious consequences. The features and advantages resulting from the use of the containment according to the first aspect of the invention and/or from the use of the continuous flow machine according to the second aspect of the invention are presented in the descriptions of the first and second aspects of the invention, where the advantageous configurations of the first and second aspects of the invention are to be considered advantageous configurations of the third aspect of the invention and vice versa.
Additional advantages, features and details of the invention are presented in the following description of one preferred exemplary embodiment and with reference to the accompanying drawings. The features and combinations of features cited in the above description and in the following description of the Figures and/or the features and combination initiatives or features found only in the Figures can be applied not only in the respective indicated combinations, but also in other combinations or individually, without thereby going beyond the framework of the invention.